Diamond abrasive blades



Oct. 1, 1957 F. A. UPPER ET AL 2,808,044

DIAMOND ABRASIVE BLADES Filed Dec. 21, 1955 LIT IN V EN TORS FREDERICK A. UPPER JAMES H. DEN TON ATTORAIELY United States atent O DIAMOND ABRAsrvn BLADES Frederick A. Upper, Niagara Falls, N. Y., and James H. Denton, Niagara Falls, Ontario, Canada, assignors to The Carborundum Company, Niagara Falls, N. Y., a corporation of Delaware Application December 21, 1955, Serial No. 554,453

9 Claims. (Cl. 125-15) This invention relates to abrasive blades for the cutting of hard materials. More particularly, it pertains to a segmental abrasive blade of the type in which a plurality of bonded diamond segments are mounted around the circumference of a slotted steel center or support and constitute the abrasive or cutting edge of the device.

Abrasive blades of the above-described type have found widespread use for cutting contraction joints in concrete highways, airport runways and the like, and are also useful in the cutting of numerous other hard materials. Improvements in the life expectancy of the abrasive segments have advanced the normal period of usefulness of the abrasive segments to the point where the life of the abrasive segments has exceeded the life of the steel center or support. As a result, failure of the blade frequently occurs because of the wearing through of the steel center just below the place where the abrasive segment is joined to the periphery of the supporting steel center. Consequently, the problem has been presented of finding some ways and means of preventing this premature eroding away of the steel center before the abrasive segments have been completely worn out.

It is therefore an object of the present invention to provide an abrasive blade embodying bonded diamond abrasive segments positioned about the periphery of a central steel support and in which the useful life of the steel center will outlast or 'at least equal or match the useful life of the abrasive segments mounted thereon.

In order that the nature of the present invention will be more clearly understood, reference is made to the accompanying drawing in which:

Figure 1 is a diametrical cross-section through an abrasive blade made in accordance with the present invention;

Figure 2 isa side plan view of a fragment of the abrasive blade shown in Figure 1, showing details of the segmented periphery and mounting of diamond abrasive segments;

Figure 3 is a side plan view similar to that of Figure 2 showing a'modified form of segmented abrasive blade embodying principles of the present invention;

Figure 4 is a side plan View similar to that of Figure 2 of an 'abrasive blade constructed according to prior art practices, and showing the manner in'which such abrasive blades havefrequently failed due to eroding away of-the steel center in the vicinity of the abrasive segments; and

Figure S is an enlarged sectional view through the line 5-5 of Figure 4. 7

According to the present invention the aforementioned problem of the early failure of the steel center of the abrasive blade before the diamond abrasive segments have been worn out or expended is accomplished by a novel and improved design of the abrasive segments of the blade. The design of abrasive segments herein described and embodying the novel features of the present invention can be used regardless of the particular bond composition used to bond the abrasive particles of the vention, each of the abrasive segments of the blade is segment together. In accordance with the presentinone leg of the abrasive segment extending along the peripheral edge of the land of the steel center upon which the segment is mounted and the second leg of the abrasive I, segment extending radially inward from the outer periphery of the steel center along one radial edge of the land. The term L-shape is to be construed broadly enough to cover a segment in which the peripheral leg of the segment has a straight inner edge or has the slight curvature required to conform to the radius of curvature of the peripheral edge of the land upon which it is mounted. While reference is made to the inwardly extending edge of the land as being radial it is to be understood that the slots between lands need not necessarily be radial but can be canted therefrom. One specific way of constructing and mounting the abrasive segment is that shown in Figures 1 and 2 of the drawing wherein the segment is shaped so as to extend beyond the leading edge of its land with an overhanging portion extending down into the adjoining slot of the steel center.

Referring further to Figures 1 and 2 of the drawing which depict one specific embodiment of the invention, the abrasive blade as shown is composed of a steel center or support 6 having a central mounting arbor hole 7 and having the periphery of the steel center 6 slotted such as by a plurality of radial slots 8 to divide the periphery of the steel center into a number of individual lands 9 extending about the entire periphery of the steel center. Mounted upon each land 9 is a bonded diamond abrasive segment 10 secured to the steel center by any suitable bonding operation such as by brazing. The bonded diamond segment 10 is slightly wider by several thousandths of an inch than the thickness of the steel center 6 so as to provide a small clearance for the steel center when the blade is used for making deep cuts into a material. The diamond segment is further shaped to provide an overhanging portion 11 which extends beyond the leading edge 12 of the land 9 and into the adjoining slot so that when the segment is brazed to its associated land the segment will extend across the major part of the peripheral surface of the land and overhang and extend down along one side of the leading edge of the land.

According to the specific embodiment of the invention shown in Figure 3 of the drawing, instead of constructing the abrasive segment and its associated land as in Figures 1 and 2 so that the segment extends beyond the edge of the adjoining slot and overhangs into the slot, the lands 12 are recessed at one end to provide a recess 14 at one side of the slot. The bonded diamond abrasive segment is then molded to a suitable shape, which is substantially of an L conformation so that the one leg of the segment will fit along the peripheral edge of the land and the other leg 11 of the segment will conform and fit into the recessed portion of the land.

It has beenfound in actual use of abrasive blades of the type herein described, such as the one shown in Figures 1 and 2, for the cutting of contraction joints in concrete that the radial leg portions 11 of the abrasive segments protect the peripheral portion of the steel center against erosion to the extent that the steel center stands up until the abrasive segments have performed their useful life. Diamond abrasive blades for such use can range in size from 10 or less, up to 24 or more in diameter, the thickness of the steel center being in the order of magnitude A to inch thick. A representative 14" diameter blade can be provided with 20 individual diamond abrasive segments mounted about the periphery, each segment being approximately two inches adjoining slot. However, the present invention is not restricted to any specific diameter of blade, or number of abrasive segments about the periphery, or specific dimensions of segment.

Figures l and picture an abrasive cutting blade embodying the conventionally designed, bonded abrasivesegments of the prior'art and showthe manner in which the peripheral land portions 1510f the steel Center are eroded away during use. This wear is-rnost severe at a point along the leading edge 16 of each land, just below the point where the abrasive segment is joined to the land and extends across the land in the area just beneath the line of attachment of the center to the abrasive segment. Wear continues at such a rapid rate that the steel center is worn through before the abrasive segment has been used to the full extent of its useful life.

In making a segmental diamond abrasive blade of the herein-described type a number of the abrasive segments of the described shape are molded from any desired composition of diamond particles and bond ingredients in accordance with conventional molding practices common and well known in the art, the particular bond composition of the abrasive segments and molding operations therefor not constituting the novel features of the present invention. For example, bonded diamond abrasive segments of the herein-described shape can be made in which the diamonds are bonded by a tungsten carbidecobalt bond in accordance with the disclosures of U. S. Patents. 1,895,926 and 1,904,049. Bonded abrasive segments of the herein described design can also be fabricated embodying the copper-tin bonds of Boyer U. S. Patent 2,137,329 or the ferrous alloy bonds of FitzaRandolph U. S. Patent 2,173,834 or Boyer et al. U. S. Patent 2,173,835. Other bond compositions well known in the art can also be used in carrying out the present invention.

In order to obtain the maximum cutting cfficiency from a given diamond content for the segments, a strong adherence of the segment to the steel center, and also otherwise accomplish the purposes of the present invention, the preferred practice in molding the arcuate hook type segments of the present invention is to provide two bond compositions made up of the same bonding ingredients in the same proportions, to one of which a chosen amount of diamonds is admixed and to the other of which no diamonds are added. A mold having a mold cavity of the desired shape for molding the arcuate segments, placed with the convex inner molding surface of the mold form facing upwardly, is charged with a small amount of the diamond-free, powdered bond mixture and lightly compacted to form a layer over the portion of the mold bottom forming the inner convex or arcuate side portion of the segment, whereupon the second bond mixture containing diamond particles is added to the mold in sufficient quantity to form the remainder of the segment. The usuahand preferred practice isto carry out the mold-filling operation so that the second bond mixture containing the diamond particles fills that part of the mold cavity which forms the radialleg or overhanging hook portion of the segment since the presence of diamonds in this portion provides the maximum protection against wear of the steel center. However, where the bond composition itself is of such character as to have pronounced wear-resistant properties, such as when tungsten carbide-based bond compositions are ,used as the bond of the diamond abrasives, the diamonds can be concentrated in the outer portion of theperipheral leg of the abrasive segment and little or no diamonds incorporeted in the radial leg portion of the abrasive seg ment. The entire mold contents, including the initial diamond-free bond portion, is then subjected simultaneously and/or sequentially to the requisite heat and pressure to compact the material and form the bonded abrasive segment. The resulting segment has the diamonds concentrated where they will do the greatest amount of cutting with a minimum loss of diamonds. Such distribution of the diamonds also improves the bonding action between the segments and the center, since it has been found that the bond composition containing no diamonds tends to form a more uniform, high strength union with the steel center than is the case with the same bond composition containing diamonds. Furthermore, the inclusion of the diamonds in the hook or overhanging portion of the segment provides a maximum amount of protection to the steel center at the areas where it normally tends to erode away.

Having formed the necessary number of abrasive segments as above described, the individual segments are secured to the steel center such as by conventional brazing techniques. Before brazing or otherwise bonding the individual abrasive segments to the peripheral lands of the steel center in the manner shown in Figure 2 with the overhanging hook or radial leg portion 11 of each segment extending along the radial side edge 12 of its land into the adjoining slot 8, the inner arcuate face of. the segment can be dressed, if necessary, so as to conform closely to the peripheral face of the land. Molding of the segment as above described with this inner convex portion of the segment relatively free of diamond particles makes the dressing operation when required much easier. Also, concentration of the greater portion of the diamond particles in the outer portion of the segment increases the cutting efficiency of the blade and utilizes more of the diamond content than if the diamonds were evenly distributed throughout the entire segment body. The diamonds embedded in the hook or overhanging portion of the segment increase its wear-resistance to impart greater protection to the land to the rear of the overhang of the segment and thus prevent the center from wearing out prematurely.

Obviously, certain minor modifications from the specific abrasive blade shown in Figure 2 and the specific compositions and manner of making referred to or described above can be undertaken without departing from the scope or spirit of the invention. For example, the slots spaced about the periphery of the steel center, although shown in radial disposition in the specific blades illustrated, can be sloped or canted from the radial direction. Furthermore, although the preferred practice is to form the diamondcontaining abrasive segment in one piece it is possible as a modification of such practice to form the arcuate or peripheral leg portion of the segment in one piece and the so-called radial leg or overhanging portion as a separate body and subsequently braze the two pieces to the steel center so as to form together a generally L-shaped or overhanging abrasive segment functionally comparable to the one-piece segment shown in Figure 2 or Figure 3.

Having described the invention in detail, it is desired to claim:

1. An abrasive blade comprising a steel center and a segmental peripheral abrasive rim, said steel center having the peripheral portion slotted to divide the periphery into a plurality of circumferentially spaced lands and intervening slots, and a bonded diamond segment bonded to the peripheral edge of each land, each of said abrasive segments having a radial abrasive leg portion along the slot side of the land extending radially inward from the outer periphery of said steel center.

2. An abrasive blade comprising a steel center and a segmental peripheral abrasive rim, said steel center having the peripheral portion slotted to divide the periphery into a plurality of circumferentially spaced lands and intervening slots, and a bonded diamond segment bonded to the peripheral edge of each land, each of said abrasive segments being substantially L-shaped with the one leg of the segment extending along theperipheral edge of said land and the second abrasive leg of the segment on the slot side of the land extending inwardly of the steel center along one radial edge of the land.

3. An abrasive blade comprising a steel center, the rim thereof being slotted radially to divide the rim into a plurality of individual lands spaced about the entire periphcry of said steel center, and a bonded diamond abrasive segment bonded to the peripheral surface and one radial slot side of each of said lands, each of said bonded abrasive segments at one end extending over and along one radial side of its land.

4. An abrasive blade comprising a steel center and a segmental peripheral abrasive rim, said steel center having the peripheral portion slotted to divide the periphery into a plurality of circumferentially spaced lands and intervening slots, and a bonded diamond segment bonded to the peripheral edge of each land, each of said bonded diamond abrasive segments being mounted on its land with an overhanging abrasive portion extending around the forward edge of said land and into the adjoining slot.

5. An abrasive blade comprising a steel center and a segmental peripheral abrasive rim, said steel center having the peripheral portion slotted to divide the periphery into a plurality of circumferentially spaced lands and intervening slots, and a bonded diamond segment bonded to the peripheral edge of each land, each of said abrasive segments extending beyond the leading edge of its land and provided with an overhanging abrasive portion extending inwardly of the adjoining slot.

6. An abrasive blade comprising a steel center having a rim composed of a plurality of lands about the periphery separated by narrow slots, and a plurality of bonded diamond abrasive segments mounted on said lands, each of said segments being slightly wider than the thickness of said steel center and mounted to extend beyond the lateral faces of the steel center and provided with an overhanging abrasive portion depending into the adjoining slot.

7. An abrasive blade comprising a steel center and a segmental peripheral abrasive rim, said steel center having the peripheral portion slotted to divide the periphery into a plurality of circumferentially spaced lands and intervening slots, each of said lands being recessed at one end, and a bonded diamond segment bonded to the peripheral edge and recessed portion of each land, each of said abrasive segments extending along the peripheral edge and into the recess portion of the land upon which it is mounted.

8. An abrasive blade comprising a steel center and a segmental peripheral abrasive rim, said steel center having the peripheral portion slotted to divide the periphery into a plurality of circumferentially spaced lands and intervening slots, and a bonded diamond segment bonded to the peripheral edge of each land, each of said abrasive segments having a radial leg portion extending radially inward from the outer periphery of said steel center, the diamond particles of the bonded abrasive segments being concentrated in the outer portion of the peripheral leg and the radial leg portion of the segments.

9. An abrasive blade comprising a steel center, the rim thereof being slotted radially to divide the rim into a plurality of individual lands spaced about the entire periphery of said steel center, and a bonded diamond abrasive segment bonded to the peripheral surface and one radial side of each of said lands, each of said bonded abrasive segments at one end extending over and along one radial side of its land, the diamond particles of the bonded abrasive segment being concentrated in the outer portion of the peripheral leg and the depending portion of the segment.

References Cited in the file of this patent UNITED STATES PATENTS 1,434,421 Arntz Nov. 7, 1922 1,699,746 McKay Jan. 22, 1929 2,064,407 Bird Dec. 15, 1936 2,065,041 Behr Dec. 22, 1936 2,088,998 Merritt Aug. 3, 1937 2,442,153 VanDerPyl May 25, 1948 2,589,357 Fantozzi et al Mar. 18, 1952 FOREIGN PATENTS 523,879 Great Britain July 24, 1940 542,054 Great Britain Dec. 23, 1941 

